Technology exists for routing communications originating from a wireless handheld telephony device through a server such as an enterprise server. This can be done, for example, to make it appear as if the communication originated from a user's place of business or to prevent a party receiving the communication from accessing the wireless user's wireless number. Often, such communications will use both an audio or voice channel for relaying a voice communication and a data channel for, for example, sending control information between the server and the wireless handheld telephony device. For example, the server may send a control command to the wireless handheld telephony device informing it of an incoming communication. Similarly, the wireless handheld telephony device may send a control command to the server requesting that the current communication be put on hold. These control commands may be sent via the a data channel when such a channel is available.
In some situations, however, a data channel between the wireless handheld telephony device and the server may be permanently or temporarily unavailable. Some current systems use means such as DTMF transmission/detection, data over SMS, USSD, etc. for relaying control or other data when a data channel is unavailable. The use of DTMF protocols and devices for non-audio signalling, however, can be slow, and creates issues concerning both missing tones and false detection of tones and is generally limited.
Similar reference numerals may have been used in different figures to denote similar components.